The thermo-physical properties of water-based NiO and NiS magnetic nanofluid were measured experimentally. Appropriately, the viscosities of 0.25 wt% and 1 wt% ZnO and NiS nanofluid were 1.03 mPa·s and 1.13 mPa·s, each greater than that of the 20?C base fluid (water), which were increased by the 7.3% and 17.7%, sequentially. The NiO and NiS nanofluid thermal conductivity increased from 0.605 and 0.618 to 0.654 and 0.693 W/m· ?C at concentrations of 0.25 wt% and 1 wt%, sequentially, when the temperature increased from the 20 to 50 ?C. The maximum thermal conductivity of the NiO and NiS nanofluid were 0.693 W/m· ?C at a concentration of 1 wt% and a temperature of 50?C. Moreover, following a solar exposure of 120 min, the photothermal energy conversion efficiency of 0.25 wt%, 0.5 wt%, 0.75 wt%, and 1 wt% NiO and NiS nanofluids increased by 4.8%, 5.6%, 7.1%, and 4.1%, sequentially, more than that of the water